The present invention relates to a direct electrostatic printing apparatus, and particularly relates to the control method and structure of an electrode device of the direct electrostatic printing apparatus.
When printing or copying a high-resolution image, we often use xerography or the so-called electrophotography, which are the most common electrostatic printing methods. By means of laser or other light source devices, the desired image is transformed to light signals, and then these light signals are given to the photoreceptor, causing potential differences on the photoreceptor where the light signal is given, thereby forming latent charged pattern image. Then, the charged colorant particles driven by sufficient electric field jump out of the cartridge device and are attached onto the surface of a photoreceptor composing the desired image. Finally, the charged colorant material is transferred to papers for printing out the final image. Because the image is first formed in the photoreceptor, and then transferred to the paper, therefore, this process is called indirect printing.
Another printing method developed later is called direct electrostatic printing (DEP). The difference between DEP and Xerography is that DEP works without the aforementioned photoreceptor, but DEP uses the electrode device with multiple apertures across itself, making the desired image by means of electric signals for establishing the electric field needed in the device, and driving the charged colorant particles through the apertures and be accumulated onto paper for forming a visible image. These electric signals do not need to be transformed into another form of energy, for example, photo energy. The main idea of DEP is to simultaneously process the colorant transfer as well as the image visualization, thereby directly showing any proper image on accepted media.
When the structure and method of the current electrostatic printing apparatus is applied on an image or photograph with varied depth levels, a group of print dots is needed to represent a single image pixel. The actual number of print dots is related to the feeling of viewing colors. In other words, there are less print dots in those of lighter shade, and more print dots would make human eyes see a darker shade. This method is widely used for depth-level images or photographs. In essence, this method sacrifices print resolution for attaining the purpose of depth levels. However, this method or structure has difficulty in changing the color depth of a single print dot. As a result, the improvement of print resolution is confined.
If a single print dot can represent a single image pixel of multiple depth-level image, i.e., the depth level of each print dot is able to be changed to correspond to the depth-level image or photograph pixel in the same color depth, it is possible to improve the print quality for depth-level images without lowering the resolution.
The purpose of this invention is to provide a control methodology and structure of an electrostatic printing apparatus for every single print dot with multi-leveled print depth in order to improve the print quality under the situation of fixed machine resolution. Moreover, the control methodology of this invention can be applied further to high resolution printing with multi-leveled print depth. Additionally, this invention is not limited to black-color printing, but also can be applied independently in the printing apparatus to color-printings of yellow, cyan and magenta, etc., and therefore provides a great support for the quality improvement in full-color printing.
This invention provides a control methodology of direct electrostatic printing apparatus, including the following steps: providing an electrode device which contains n layers of electrode layer for representing (n+1) levels of print depth, and at least an aperture passing through; and while the mth level of print depth in the total of (n+1) levels of print depth is printed, applying the voltages to the total of m layers of electrode layer, thereby driving a charged colorant particle from a cartridge apparatus to pass through the aperture(s) and to be attached onto the corresponding print dot of a recording medium.
This invention also provides a control methodology of a direct electrostatic printing apparatus, including the following steps: providing an electrode device which contains n layers of electrode layer representing 2n levels of print depth, and at least an aperture passing through; and while the mth level of print depth in the total 2n levels of print depth is printed, applying a binary-composed voltage set to the corresponding n layers of electrode layer, thereby driving a charged colorant particle from a cartridge apparatus to pass through the aperture and to be attached onto the corresponding print dot of recording medium.
This invention also provides a control methodology of a direct electrostatic printing apparatus, including the following steps: providing an electrode device which contains n layers of electrode layer for representing k levels of print depth, where 3xe2x89xa6kxe2x89xa62n, and at least an aperture passing through; and while the mth level of print depth in the total of k levels of print depth is printed, applying an arithmetic-composed voltage set to the corresponding n layers of electrode layer, thereby driving a charged colorant particle from a cartridge apparatus to pass through the aperture and to be attached onto the corresponding print dot of recording medium.